Bill Fitzmaurice

Odd how often this subject comes up. My car has a top speed of 130mph, yet the speed limit is only 75. How does one deal with that issue? [i]Don't put the pedal to the metal. [/i]Seems obvious to me. BTW, clipping can toast tweeters, but has absolutely no effect on woofers. Sometimes even those who really should know better don't.

[quote name='Skybone' timestamp='1435531053' post='2809837'] if a 4 x 10 cab has an 8 ohm rating (ie, 4 x 8 ohm speakers), would it be possible to rewire it so that it would become a 4 ohm cab, without changing the speakers? [/quote]As explained above, no. And if the reason is the usual 'to get all the watts out of my amp', it wouldn't matter anyway.

[quote name='Dan Dare' timestamp='1434827917' post='2803182'] Don't worry about wattage, etc. Speakers can handle much higher than stated ratings in short bursts. [/quote]With a few exceptions thay cannot handle even half their rated power before they'll distort, so if you don't push them so hard they they are distorting you'll be nowhere near their power capacity. That's where the volume control comes into play [quote]You're more likely to cause damage by under-driving a cab.[/quote]That would be fostering the myth of underpowering. There's a reason why it's a myth.

I ran a 3500 for ten years, never any problem, always sounded good. I only sold it because it weighed a ton. Or is it tonne?

[quote name='ubit' timestamp='1434460037' post='2799777'] I find when we play, I hear everything clear as hell. As the night goes on, even though nothing is changed, I find everything becomes a wall of noise and I struggle to hear myself or the other instruments clearly. I realise our ears start to filter out certain frequencies and it's probably down to us being too loud at the back line. [/quote]+1. Your ears will lose sensitivity as a protective reflex when exposed to constant high sound levels. This is why you seem to be softer at the end of a set, and why when you take a break and then go on again it seems louder than just before the break, as during the break hearing sensitivity is restored. One way to address the apparent loss in volume with time is to play louder, which only makes things worse. The smarter route is to either play at lower volume or use earplugs. Better that than eventually needing to use hearing aids.

[quote name='Jenny_Innie' timestamp='1434450680' post='2799621'] I went from kickass bad girl growl to dull beardy geography teacher in corduroys mush. Not very punk. [/quote]Growl can come from two sources. One is pushing the amp into clipping, the other is pushing the speaker into clipping. If the amp and/or the speaker has a lot of available headroom then you might not be able to get growl without being too loud for a given room. You might be able to get what you want by turning down the amp master, or by running only one cab, or by using a pedal or rack device. You also may find that Barefaced isn't the best cab for you, as they tend to have a lot of headroom. If you do decide to downsize a small valve amp, 35 to 50 watts, may give you what you're after.

[quote name='xgsjx' timestamp='1433257114' post='2789478'] Why 2 different cabs? [/quote]Probably because he thinks that the 1x15 will give better lows and the 2x10 better highs. Sometimes that's true, but only sometimes, and even if there's a difference it's usually slight. I'd do two vertically stacked 2x10s myself.

Based on your description I wouldn't be concerned unless the winter temperatures in the shed regularly go below freezing. That in itself isn't an issue, it's the condensation that will form when you return the gear to a warm space that will.

[quote name='Iain' timestamp='1432816905' post='2785245'] Is this a useful rule for front-ported cabs as well or more so for rear-ports? [/quote]The port location doesn't matter. The boom frequencies tend to be centered in the 100-160Hz range, port output tends to be centered around 50-60Hz. From the standpoint of boundary loading off the wall that requires the source be less than 1/4 wavelength distant. 1/4 wavelength at 60Hz is 4.7 feet. Wnen it's exactly 1/4 wavelength theres a cancellation notch. For instance, having the cab front 2.3 feet from the rear wall would notch the response around 120Hz, while below that would be unaffected, be it front or rear ported.

[quote name='Beer of the Bass' timestamp='1432737942' post='2784430'] I've played around with boundary reinforcement when playing unamplified double bass - I've found that standing as far into the corner of the room as possible seems to give me a little extra low end. [/quote]A wavelength is a wavelength, no matter what the source.

[quote name='FuNkShUi' timestamp='1432733001' post='2784362'] I am guessing having the sound closer to ear level is a good thing, but having it off the floor, does that effect its perceived sound? Do i lose anything by doing this? There was a thread a little while back where someone posted a picture of their cab which was perched on what looked like a keyboard stand (cant remember exact thread sorry). That's what got me thinking..... I have a 2X10 setup now, and wondered if this kind of thing would benefit or hinder me? [/quote]You'll start losing floor coupling at about 2.5 feet off the floor, so don't go higher than that. If it's still hard to hear tilt it back. A keyboard stand is a bit too high. The same applies to the distance to the wall behind the cab. Placing the front of the cab more than 2 feet from the wall will not only reduce boundary reinforcement off the wall, it will cause a response dip. That can be of use on boomy stages. The correct distance from the wall can put the dip at the boom frequency, cancelling out the boom.

[quote name='Marvin' timestamp='1432729550' post='2784322'] Turning to a 210 bass cab, not the BF retro as that's a bit different. At what sort of frequency does dispersion become an issue for a 210 cab? And how important are these frequencies, if at all, to most bass player's tone?[/quote]If you mean by placing drivers side by side, where comb filtering is concerned they should not be more than one wavelength center to center. With a pair of tens set 11 inches center to center that's 1.2kHz, right smack dab in the middle of the midrange. From there on up comb filtering will occur. Even below that frequency side by side drivers has an effect. The dispersion angle below the 1 wavelength center to center distance is more than halved compared to a single driver. At 100Hz, where dispersion is nominally 360 degrees anyway, that's not an issue. At 800 Hz, where dispersion of a single driver may be 180 degrees or less, it's not the best scenario. If I was to make a .5 alignment using tens I'd low pass the second driver around 500Hz. Since some 75% of the power bandwidth lies below 500Hz there's no need to use both drivers higher than that.

[quote name='davedave' timestamp='1432670005' post='2783870'] Hi Bill. Cheers for getting in touch. I've certainly got a mountain to climb with this project. I'm looking forward to the challenge though. Is there any reading you can recommend on the theory side to get me going please? All help is much appreciated. [/quote]There's a lot to be found here: http://billfitzmaurice.info/forum/viewforum.php?f=18

I use WinISD Pro (7) and HornResp. Coming up with the numbers is virtual child's play. Translating the numbers into a viable design is where the work lies.

[quote name='warwickhunt' timestamp='1432572792' post='2782834'] The only flaw being that a pair of such cabs stacked vertically would, by default, have the full range drivers (one from each pair) together as the centre pair of a vertical line of 4. [/quote]That it would. It's not a flaw. There's even a name for that driver configuration, the W-M-M-W, altough in this case the Ms (midrange) would be full range, not pure midrange, drivers. [quote]Always thought vertical was a myth for low frequencies[/quote]It would be, which is why I have never promulgated that notion. But it's all a matter of scale. While no sensible bass rig would ever be large enough for low frequencies to be affected in a major way by horizontal versus vertical placement, it could be a concern with a large PA system. A dozen or more large subs arranged side by side across the front of a stage would be an example, unless it was the operators intent in so doing to limit the horizontal dispersion of the array.

[quote name='warwickhunt' timestamp='1432566639' post='2782727'] So they are horizontally aligned in the cab but for superior/best results should really be used vertically? [/quote]If you put a single cab horizontal the full range speaker is playing to your calves, not your ears. If you stack a pair horizontally that's not bad, but stacked vertically places the uppermost full range driver closer to your ears, which is better. But you want the full range drivers adjacent, if separated you introduce combing and cancellation issues on the vertical plane. That won't bother the audience, being too far away to be affected by it, but it will make what you hear quite different from what they hear.

[quote name='warwickhunt' timestamp='1432375946' post='2780927'] Puzzled! I thought you (among many) always advocated the vertical stacking of drivers as the horizontal was an inferior/flawed design and that the 'science' behind the reason was pretty conclusive. So are you saying that horizontal is as good as vertical... so long as there is a well designed cross-over? [/quote]It's not a crossover in the usual sense between a woofer and tweeter. Only one of the tens runs in the upper frequencies, so there are no cancellation issues. The two drivers operate in tandem only in the lows, where the wavelengths are long enough that the two drivers will only compliment and never fight each other. Still, if using one you should have it vertical, with the full range driver on the top. When using two they'll work best vertical, mirror imaged, so that the two full range drivers are adjacent.

[quote name='chris_b' timestamp='1432315128' post='2780435'] ...you are constantly telling people that what they hear and like is wrong because the science says it isn't right. [/quote]Show me where I did so. Please. Just once I'd like to see proof of what I'm accused of. Or ignore me. But do me the courtesy of not putting words in my mouth.

[quote name='chris_b' timestamp='1432295127' post='2780104'] This is the usual tedious one-sided tug-of-war. One side thinks the text book is more important than your ears and shouts down anyone who disagrees or thinks that ears are more important. [/quote]Show us an example. The only 'shouting' I've seen is from those who say that what they hear, or what they think that they hear, is all important, and that the science behind it is irrelevent, if not flat out wrong. Innumerable scientists have had to suffer this same nonsense, no matter what their field of study, going all the way back to Aristotle, extending right through to Hawking. If you don't understand how gear works and have only your ears to rely on that's all well and good. You don't have to be Enzo Ferrari to know how to drive a Ferrari. You do have to be Enzo Ferrari to invent the Ferrari.

You probably would have to open it up to find identifying markings. It's probably not a Silvertone, unless there was a UK company that used that name. In the US Silvertone was a store brand sold by Sears-Roebuck, many rebadged Coral and Danelectro, but not in the 1950s.

The K140 will give best results in a 2 cu ft (net) box tuned to 30Hz. A single 3 inch ID tube 8 inches long will suffice, as with the 150w power handling it won't create sufficient port velocity to result in chuffing.

[quote name='Conan' timestamp='1431586953' post='2772752'] Surely this thread is now a perfect example of irresistible force meeting immovable object? The two "sides" are so intransigent and convinced of their "correctness" that they won't listen to the other. [/quote]The interpretation of what the two 'sides' stand for depends on which you're on. Those on the purely subjective side who deny the benefits of objectivity make the assumption that engineers wear white coats, work in laboratories, and wouldn't know an E string from a pickup. I don't own a white coat, and I don't have a laboratory. My work clothes are well imbedded with sawdust, as is my 'office'. I don't know how long Alex has been a bassplayer, but I have been since 1965, and not immodestly would put my chops and ears up against [i]anyone[/i] elses. Just because I know how gear works doesn't mean I don't know how to use it.

[quote name='Beer of the Bass' timestamp='1431462152' post='2771687'] If this isn't too much of a digression, it's notable that those specific EVM and JBL drivers are much appreciated by bassists who often claim to get something from them which they're not hearing from a lot of more modern drivers. Which specific properties from a technical perspective might be responsible for that? You've been quite clear that transient response isn't it, but what [i]is[/i] it? [/quote]The main difference between a vintage EMV or JBL and most modern drivers is the Qes, which is basically the effective magnet strength. The lower the value the higher the effectivemagnet strength. Anything below 0.35 is considered low by modern standards. The EVM 15L is 0.25, the JBL E140 is 0.19. Very low Qes results in high sensitivity in the mids, but it also chokes off the low end response. The EVM15B is better, at 0.3. Its main limitation is the result of the short 3.3mm xmax. Today drivers with twice that xmax are common, and that translates to needing two 15B to get the same output as one good modern fifteen, or you can get as much output from a modern twelve as a 15B. Note that what many might think is better transient response with these drivers is actually less low end content. What might be mistaken for poor transient response in modern electric bass drivers may actually be more low frequency capability. Another possibility is with very high Qes drivers, 0.5 and higher, which are common in cheap cabs. They tend to be boomy in the midbass, which can be mistaken for poor transient response. Poor transient response is a common trait of subwoofers, but you shouldn't be using subwoofers in the midrange where poor transient response would be evident anyway. If you know what you're looking for in the specs you can find modern drivers that sound like vintage EV and JBL. The Eminence EPS 15C, for instance, nearly duplicates the EVM15B. But having the same 3.3mm xmax it doesn't quite make it as an electric bass driver by todays standards. They market it for pedal steel guitar. The EPS 12C nearly duplicates the EVM 12L, it's also marketed for pedal steel.

[quote name='vailbass' timestamp='1431438328' post='2771337']Here's a great example of how choosing a speaker on specs alone would be a major mistake; the EVM 15" speakers that I love are rated for 100 watts! [/quote]No professional loudspeaker designer, nor talented amateur for that matter, gives much attention to watts. Of the dozen odd driver parameters that are pertinent watts are possibly the least significant. This is just another example of those arguing against the science not understanding the science. The difference between a player who doesn't bother to learn the science and one who does is that the former knows that the EVM sounds good, the latter knows why.

[quote]Both cabs will get 250w.[/quote]That's probably not the case. Power distribution is a far more complicated issue than simple division. For that matter power delivery into a single cab isn't a constant. It varies with impedance, and impedance isn't a set value, it's different at every frequency. A typical 8 ohm rated speaker will have an actual impedance that may range as low as 5 ohms and as high as 50 ohms.[quote]Even if you run the amp at full chat, neither of them will receive enough watts to cause any damage .[/quote]Also not the case. Most speakers cannot take anywhere near their thermal rating before mechanical damage is a possibility. Most amps can put out at least four times their rated power for short duration peaks, and most will put out twice their rated power long term with high THD, as their power ratings are measured at low THD. The key to preventing damage is simple enough,though. If the speakers distort, turn it down.